Transcript Chapter 12
Chapter 12 Flexibility The importance of flexibility • For health: – contributes to efficient movement in walking and running – Prevents or relieves aches and pains as one ages • For athletics: – Need for flexibility in specific joints, which varies with athletic activity (e.g., hurdler needs hip flexion and extension flexibility) Factors that limit flexibility • Bony structure (e.g., knee or elbow) • Soft tissues, including muscle and connective tissue (e.g., ankle or hip) Physical properties of stretching theory • A low-force stretching method requires more time to produce a given elongation than does a higher-force method. • The proportion of elongation that remains after stretching is greater with a low-force, longduration stretching than with high-force stretching. • The amount of structural weakening produced by a given amount of tissue elongation varies inversely with temperature. Static versus dynamic flexibility • Static flexibility – The measure of range of motion • Dynamic flexibility – Reflects joint stiffness and resistance to limb movement – Limited by elasticity and plasticity of the joint and muscle Visit Types of Stretching at www.bath.ac.uk/~masrjb/Stretch/stretching_4.html Stretch reflexes • A muscle that is stretched with a jerky motion responds with – A contraction (stretch reflex) • A muscle that is stretched with a steady, static stretch invokes the – Inverse myotatic reflex Static and ballistic stretches • Ballistic—bouncing movements in which one body segment is put in movement by active contraction of a muscle group and the momentum is then arrested by the antagonists at the end of the range of motion • Static—held stretches that involve holding a static position for 30 to 60 seconds, during which specified joints are locked into a position that places the muscles and connective tissues passively at their greatest possible length Examples of ballistic stretching methods 1. Trunk lifter. a. Hands raised behind neck. b. Raise head and chest vigorously. c. Partner holds feet. 3. Trunk bender. a. Legs apart and straight. b. Hands behind neck. c. Bend trunk downward in a bouncing fashion. d. Keep back straight. 5. Trunk rotator. a. Arms extended laterally. b. Twist to left and then to right. 7. Single leg raiser. a. Front leaning rest position. b. Keep feet in extended position. c. Raise one leg at time. Alternately. 2. Leg lifter. a. Arms down at side. b. Raise both legs off floor and return vigorously. 4. Upper back stretcher. a. Legs crossed, sitting position. b. Try to touch head to floor. c. Use vigorous bouncing motion. 6. 8. Gastocnemius stretcher. a. Stand on raised surface on balls of feet. b. Lower weight and return rapidly. c. Use partner to balance if necessary. Arm and leg lifter. a. Supine position, arms and legs extended. b. Whip arms and legs up and down alternately. c. Right arm and left leg come up simultaneously and vice versa. Advantages of static stretching • There is less danger of exceeding the extensibility limits of the tissues involved. • Energy requirements are lower. • Static stretching does not cause muscular soreness. Examples of static stretching methods 1. Upper trunk stretcher. a. Keep pelvis on floor. b. Extend arms. 2. Lower trunk stretcher. a. Grasp ankles from behind and pull. b. Hold head up. 3. Lower back stretcher. a. Legs extended-toes pointed. b. Grasp outer borders of feet and pull head downward. 4. Upper back stretcher. a. Raise legs up and over head. b. Rest extended toes on floor. c. Leave hands and arms flat on floor. 5. Trunk twister. a. Turn at trunk. b. Turn head in direction of trunk. 7. Toe pointer. a. Sit on feet, toes and ankles stretched backward. b. Raise knees from floor slightly. c. Balance weight with both hands on floor just behind hips. 6. 8. Gastrocnemius stretcher. a. Feet 3 to 4 feet from wall. b. Keep body straight. c. Keep feet parallel and heels on floor. Shoulder stretcher. a. Bring right hand to upper back from above. b. Bring left hand to upper back from below and hook fingers of the two hands. c. Repeat on other side. Proprioceptive neuromuscular facilitation (PNF) • Stretching a muscle immediately after a maximal contraction • Contract-relax or contract-relax with agonist-contraction stretching techniques Visit PNF Stretching at www.sport-fitness-advisor.com/pnfstretching.html Example of contract-relax (CR) proprioceptive neuromuscular facilitation (PNF) stretching method 1. Lie on your back and place towel around the bottom of one foot. 2. Fully straighten leg, lift until you feel moderate resistance. 3. Contract hamstring muscle for 5-10 seconds. 4. Pull on the towel to further stretch the hamstring muscle. General guidelines for designing static or PNF stretching programs • Select one or more stretching exercise for each muscle group to be trained. • Slowly increase the force of the stretch to a point of mild to moderate discomfort. • Hold this position for 30-60 seconds. • If used, proceed with PNF methods. • Repeat the stretch two to three times. • Total stretching program normally takes 15 to 30 minutes. Visit Flexibility and Stretching Web Links and http://sportsmedicine.about.com/cs/flexibility/ Factors affecting flexibility • • • • • Activity Weight training Gender Age Temperature Visit Flexibility Basics at www.fun-and-fitness.com/info-zone/flexibility.html